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Structural and electrical investigation of amorphous-to-crystalline transformation in iron disilicide alloy thin films

Published online by Cambridge University Press:  31 January 2011

M. Michelini
Affiliation:
Physics Department of Modena University, Via Campi 213/A, I-41100 Modena, Italy
F. Nava
Affiliation:
Physics Department of Modena University, Via Campi 213/A, I-41100 Modena, Italy
E. Galli
Affiliation:
Mineralogy Institute of Modena University, Via S. Eufemia, I-41100 Modena, Italy
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Abstract

Electrical and structural properties of coevaporated Fe–Si thin alloy films as a function of annealing temperature have been studied by in situ electrical resistivity measurements and structural analysis including 2 MeV 4He+ ion backscattering, x-ray diffraction, scanning microscopy, and roughness measurements. In the as-deposited state the coevaporated alloy film was amorphous. Upon annealing a sharp increase in resistivity occurred near 400 °C and the increase was determined to be amorphous-to-crystalline β–FeSi2 phase transformation. In cooling, the resistivity increased monotonically with decreasing temperature. Surface roughness is well pronounced for films heat treated at temperatures higher than 700 °C and is due to the difference in thermal expansion coefficients of substrate and β–FeSi2. The crystalline β–FeSi2 was determined to be a semiconductor with an energy gap of 0.80 eV. It is p-type, having a hole concentration and a Hall mobility of 1.4 × 1018 cm−3 and 4 cm2/V s, respectively, at room temperature. The kinetics of the transformation was determined by isothermal heat treatment over the temperature range of 362 °C to 390 °C, and an activation energy of 2.3 eV was measured. The nucleation and growth kinetics in the crystallization process show a change in the power of time dependence from 2.1 to 3.4.

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Articles
Copyright
Copyright © Materials Research Society 1991

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